Unless you only write flash fiction and the extent of your piece is a mere 50/100 words, you probably create a great many words. An article might be 1,000/2,000 or more and a book likely certainly consists of tens of thousands of words; indeed the very volume of words might be a problem in getting it written.
But length is a luxury that you do not always have. If there is one thing that communications aiming to sell your work need to be it is brief. Actually succinct is a better word because what you want to say needs to be well encapsulated. This needs some planning. Think of everything you could say and be ruthless. Concentrate on the essentials; though some of what you say may hint at there being more that could be said. Signpost what you are doing using phrase like: ‘briefly…’; ‘the essentials are…’ Write tight, edit and write tighter. Of course, you must not be so abrupt as to be rude, some courtesy is necessary, but frills are not, especially comments that stray far from your core suggestion. Apply this approach throughout the text you aim to send: a brief introductory letter/cover sheet, a brief description of your suggestion, a brief biographical note if such is appropriate. Make sure the various elements flow together and reflect your original plan of what you wanted to say and emphasise.